美国国家公共电台 NPR Studying The Ripple Effects Of Shrinking Arctic Sea Ice（在线收听）

LULU GARCIA-NAVARRO, HOST:

Arctic sea ice is one of the most dramatic indicators of the changing climate. Some months, the ice cover on the Arctic Ocean is about half of what it was decades ago. And its thickness has shrunk substantially. Changes in the ice may also mean a host of other changes in the Arctic system and around the globe. To better understand this, scientists have frozen an icebreaker alongside an arctic ice floe that they will observe for a whole year. And that's where our reporter Ravenna Koenig caught up with them.

RAVENNA KOENIG, BYLINE: Out on an ice floe about 5 degrees from the North Pole, a bunch of scientists are setting up equipment. It's part of a project called MOSAiC, or the Multidisciplinary Drifting Observatory for the Study of Arctic Climate. And the primary question they're trying to answer is, what are the causes of diminishing Arctic ice? And what are the consequences? Ocean physicist Tim Stanton stands surrounded by boxes of tools and equipment, next to a hole in the ice, about 15 miles from where the MOSAiC ship is frozen in.

TIM STANTON: OK. I've got to just get the hairdryer.

KOENIG: Ooh, a hairdryer?

STANTON: Well, it's a electrical - what do you call it? - heat gun. It'll frizz your hair, that's for sure.

KOENIG: It's about 18 degrees Fahrenheit. And the heat gun is for warming up electrical connectors on a science buoy.

(SOUNDBITE OF HEAT GUN WARMING)

KOENIG: Stanton is in the middle of a grueling eight-hour process to install the buoy. It will operate independently out here throughout the year, collecting data from all sorts of scientific bells and whistles that hang below it in the water.

STANTON: The flux package mounts on here. And that's what measures the transport of heat, salt and momentum in the water column.

KOENIG: Here is why Stanton's interested in those things. As more sea ice melts in the summertime, it's contributing fresher water to the top of the ocean. The saltier ocean water, which sits lower because it's more dense, can create a barrier that prevents the fresher water from going down. If that top water is trapped near the surface, Stanton thinks it can absorb a lot more heat from the sun and lead to even more melting of the ice.

STANTON: You can get these fresh, warm layers that - when a little bit of wind comes along, does a little bit of mixing - really melts the heck out of the ice.

KOENIG: He thinks this might play an important role in why the sea ice is disappearing as fast as it is. While Stanton is asking questions about things that are going on below the ice, other scientists are looking at things going on above it, like Jessie Creamean, who's out on the ice testing a device that collects tiny particles from the atmosphere called aerosols.

JESSIE CREAMEAN: Little aerosol sampler. Do well today.

KOENIG: No, we're not talking about the ones in hairspray. Aerosols can be dust, pollen or fungi. And they're the seeds that clouds need to grow. And in the Arctic, scientists think that they can also come from tiny organisms in the water, like bacteria or algae. Less ice on the ocean could mean more aerosols getting blown from the water into the atmosphere and seeding more clouds.

CREAMEAN: My hypothesis is from open water sources, we get generation of these particles from microbes in the ocean.

KOENIG: There's a lot that scientists still want to find out about clouds in the Arctic. But one thing they know is that they're important for regulating temperature - kind of like a thermostat. Depending on the season, whether the clouds are over water or ice and the features of the clouds, they can wind up cooling or warming the Earth below them.

CREAMEAN: That affects how much heat can basically help melt the sea ice. Or it can actually reflect sunlight from the sea ice. So it has a big role in controlling how much sea ice we have here.

KOENIG: Creamean and Stanton are two among hundreds of scientists from different disciplines who are trying to better understand how different parts of this changing region work.

MATTHEW SHUPE: How the atmosphere interacts with the sea ice, how the ocean interacts with the sea ice, the ecosystem, the bio-geochemical processes.

KOENIG: That's Matthew Shupe, an atmospheric scientist and one of the coordinators of the expedition. So why do scientists need to know all this?

SHUPE: This whole project is aimed at improving our models.

KOENIG: When Shupe says models, he means the computer simulations scientists use to get estimates for things like how much the earth could warm in the next 50 years. The better you reflect reality in those simulations, the better a prediction you'll get. But because so little is known about the Arctic ice system, Shupe says that the predictions for how it will respond to climate change vary a lot.

SHUPE: The Arctic is a place where the models agree the least. So that tells us that we're missing something.

KOENIG: Improving the models will help forecast things like when the Arctic Ocean might have its first ice-free summer, how quickly the globe is going to warm as a whole and how the melting Greenland ice sheet will add to global sea-level rise. By observing how all the little pieces of the system fit together over the next year, scientists hope they can bring that big picture into clearer focus. For NPR News, I'm Ravenna Koenig in the central Arctic Ocean.